Stator vane assembly for axial-flow fluid machine



M y 1961 HAWORTH ETAL 2,982,519

STATOR VANE ASSEMBLY FOR AXIAL-FLOW FLUID MACHINE Filed Feb. 1, 1957 2 Sheets-Sheet 1 15 I 53 22 i5 55 15a 1m 1/ 77 mafia +2 $3 y 2, 1961 L. HAWORTH ET AL 2,982,519

STATOR VANE ASSEMBLY FOR AXIAL-FLOW FLUID MACHINE 2 Sheets-Sheet 2 Filed Feb. 1, 1957 United States Patent Of STAT OR VANE ASSEMBLY FOR AXIAL-FLOW FLUID MACHINE Lionel Haworth, Littleover, and Ralph John Shire, Normanton, England, assignors to Rolls-Royce Limited, Derby, England, a British company Filed Feb. 1, 1957, Ser. No. 637,758 Claims priority, applicationGreat Britain Feb. 13, 1956 Claims. (Cl. 253-78) This invention comprises improvements in or relating to stator vane assemblies, such for instance as are used in axial-flow fluid machines for example in axial-. flow turbines of gas-turbine engines.

In such stator vane assemblies for axial-flow machines, it is common to provide a tubular casing and to mount the stator blades individually in the casing through interengaging parts on the casing and on the root platforms of the blades. When the casing is fully annular, ie it is not made in say two sections abutting on a diametral plane, it is necessary to provide such parts which can be engaged by a generally axial insertion of the blade and which co-operate' to prevent radial and circumferential displacement of the blades. Thus in one known construction of nozzle guide vanes for axial-flow turbine, the guide vanes are provided at their outer ends with platforms which subtend equal angles at the axis of the turbine, the circumferentially-spaced end faces of which platforms are planes containing radii through the axis of the machine so that the end faces of each platform are inclined to one another at the angle subtended by the platform, and the means for retaining the blades circumferentially in position comprises flanges projecting inwardly from the casing and having parallel-sided notches machined in them, which notches are engaged by parts formed on alternate platforms by machining awayportions of the end faces to afford on each' of the alternate platforms a pair of parallel flats to co-operate with the parallel sides of a notch.

This invention has for an object to provide a stator vane assembly whereby manufacture is simplified and which hasadvantages in use.

According to the present invention, a stator vane assembly for example for an axial-flow machine, comprises a fully annular casing and a plurality of stator blades each having a blade platform at its outer end, each of a number of said platforms having its circumferentially-spaced end surfaces parallel and projecting into a corresponding one of an equal number of circumferentially-spaced parallel-sided notches in the casing, and each of the remaining platforms having plane end surfaces inclined to each other at such angles that when the blades are assembled in the casing, the platforms for a complete annulus with the end surfaces of the platforms in contact.

Preferably each alternate platform has its end surfaces formed as planes parallel to a radius from the turbine axis through the centre point of the platform, and thus the corresponding notch in the casing will have its sides parallel to this radius, and the end surfaces of the intermediate platforms which abut the platform will also be parallel to this radius. Consequently the circumferentially-spaced end surfaces of each intermediate blade will be formed as planes inclined to one another at an angle equal to that between the radii through the centre points of two adjacent parallel-sided platforms.

It will be appreciated that in constructions according to the present invention the outer annular casing receives the torque reaction from the blades through the spaced parallel-sided notches, and it is an important feature that these notches may be milled or broached either parallel with the axis of the assembly or on a helix. A slot thus formed takes the torque reaction from the blade of which theplatform engages with the notch, together with the torque reaction of the adjacent blade or blades. A further advantage of the invention presented by the provision of parallel-sided notches in the casing is that radial expansion of the blade may be accommodated within the radial extent of the notch without varying the circumferential clearance of the blade platform in the notch.

One construction according to this invention will now be described with reference to the accompanying drawings, in which Figure l is a section through part of the nozzle-guide vane assembly of an axial-flow turbine of a gas turbine engine, the plane of section being normal to the axis of the engine,

Figure 2 is a section on the line 22 of Figure l and has the section line for Figure 1 indicated on it at 1--1, and

Figure 3 is a section on the line 3--3 of Figure 1.

Referring to the drawings, the main fully annular casing of the turbine is indicated at 10 and it has mounted:

within it a number of rings of nozzle-guide vanes of which one ring is shown.

Each nozzle-guide vane comprises a vane portion 11, an inner platform 12 and an outer platform. The outer platforms are alternately referenced 13 and 33 and they afford means by which the vanes are mounted in the cas-' ing 10.

It is arranged that the guide vanes can be inserted into the casing 10 with a generally axial movement from the downstream end of the casing and it is further arranged that when the vanes are in position they are held against axial, circumferential and radial displacement.

The platforms 13, 33 areprovided on their outer surfaces each with radial projections 14 which extend circumferentially across the platformsand which have at their radially outer ends axial flanges 15 which engage in axially-facing peripheral channels 16 formed in internal circumferential ribs 17 on the inner surface of the,

casing 10. The blades are thus located radially.

At its downstream end each platform 13, 33' is provided with an axial extension 18 having at its downstream edge a radial flange portion 19, andwhen the nozzle-guide vanes are assembled in position the flange portions 19 lie between a pair of rings 20, 21 of selected axial length which position the guide vanes axially of the:

casing and prevent their axial displacement.

In order to locate the nozzle guide vanes against circumferential movement, the ribs 17 are each formedlwith a radially-inwardly projecting flange 22 in which a number of parallel-sided notches 23 are cut, the notches be, ing equally spaced around the flange 22 and the number of notches being equal to half the number of nozzle guide vanes 11.

The platform 13 of each alternate nozzle guide vane has its circumferentially-spaced end surfaces 13a formed as planes parallel to one another and to the radius 13b from the axis of the turbine through the centre of the platform 13, and the spacing of the end surfaces 13a is such that the platform can slidingly engage within a notch 23. The corresponding end surfaces 12a of the I l atented May 2, 1961 ferential extent that the surfaces 33a are, when the vanes are assembled in contact with the surfaces 13a of the platforms 13 on each side of it, and since the end surfaces 13a of the alternate platforms 13 are parallel to their respective radii 13b, the surfaces 33a of the remaining platforms 33 are inclined to one another at an angle equal to the angle between adjacent radii 13b.

It will be seen (Figure 3) that the radial projections 14 of the platforms 33 are cut away over their whole circumferential dimension as compared with those of the platforms 13 which engage the notches 23, so as to accommodate the portions of the flange 22 between the notches 23. V

p The end surfaces 120 of the inner platforms 12 of the vanes 11 having platforms 33 are contained in the same planes as the end surfaces 33a and thus the end surfaces 12c and 33a of these platforms can be machined in a single operation.

As will be seen from Figure 1, the platforms 13, 33 together form a complete annulus.

The end surfaces 12a, 12c, 13a, 33a may lie in axial planes, or may as shown lie in planes which are inclined to planes passing through the axis of the nozzle guide vane assembly.

It will be appreciated that by machining the two end surfaces 120, 13a of each alternate nozzle guide vane parallel to one another, the width of the vane can be more easily controlled to close limits, and thus the leakage between adjacent vanes may be reduced.

We claim:

1. A stator vane assembly comprising a fully annular casing an a ring of circumferentially-spaced stator blades supported within said casing to project radially inwardly therefrom, each of said stator blades being separately mounted in the casing, said casing having internally thereof a circumferential flange having formed in it a number of notches which is less than the number of said stator blades, said notches being equi-angularly spaced around the casing and each of said notches having a pair of parallel circumferentially-spaced side walls which are parallel to a plane containing the casing axis and a radius drawn from the casing axis through a point circumferentially midway between the pair of walls, each of a number of said stator blades equal to said number of notches having at its outer end a blade platform which has a pair of circumferentially-facing parallel surfaces having a circumferential spacing equal to the spacing of the side walls of a notch, said blade platforms each projecting radially into a corresponding one of the notches with the parallel surfaces contacting the side walls, and the remaining stator blades having at their outer ends blade platforms which extend circumferentially between the parallel-surfaced platforms and have circumferentially-facing surfaces in contact with the adjacent circumferentially-facing surfaces of said parallel-surfaced platforms, and each of said stator blades having at its inner end a blade platform having circumferentiallyfacing surfaces which are co-planar with the circumferentially facing surfaces of the outer platform.

2. A stator vane assembly according to claim 1, where- 6 in each alternate platform has its end surfaces formed as planes parallel to an axial plane containing the turbine axis and a radius from the turbine axis through the centre point of the platform, and the corresponding notch in the casing has its side walls parallel to this radius, and the end surfaces of the intermediate platforms which abut the platform are parallel toithe axial plane, and circumferentially-spaced end surfaces of each intermediate blade are as planes inclined to one another at an angle equal to that between the axial planes through the centre points of two'adjacent parallel-sided platforms.

3. A stator vane assembly comprising a fullyannular casing and a ring of stator blades, each separately mounted in the casing, each of said stator blades having an outer blade mounting platform and an inner blade mounting platform, said casing including parts defining a series of circumferentially-spaced notches, there being one such notch radially in line with each alternate stator blade of said ring of stator blades, each notch having a pair of circumferentially-spaced parallel side walls, the inner and outer blade mounting platforms of each of said alternate stator blades having circumferentiallyand oppositely-facing plane end surfaces which are parallel and are spaced apart by a distance equal to the spacing of the side walls of the aligned notch and the outer platform of each of said alternate stator blades projecting radially into the aligned notch thereby to locate the said alternate stator blades circumferentially in the casing, the correspondingly facing plane end surfaces of the inner and outer platforms being co-planar, and the inner and outer mounting platforms of the remaining stator blades having circumferentially and oppositely-facing spaced plane end surfaces of which correspondingly facing end surfaces are contained in common planes, the angle subtended between the common planes of the end surfaces of each of said remaining stator blades being equal to the angle subtended between the adjacent end surfaces of the said alternate stator blades on each side of it and the end faces of the platforms of the said remaining blades abutting the end faces of said alternate blades whereby said remaining blades are located circumferentially.

4. A stator vane assembly as claimed in claim 3, in which said plane end surfaces of said inner and outer platforms of each of said alternate stator blades are parallel to a radius from the axis of said casing through the centers of said blade platforms, and the aligned notch in said casing having its side walls also parallel with said radius.

5. A stator vane assembly as claimed in claim 3, in which each of the outer blade platforms is provided with a plurality of axially-spaced axial projections engaging recesses defined in said casing, said axial projections all extending in the same direction, and radial projections for engagement in further recesses in said casing whereby said platforms are located radially and axially with respect to said casing.

References Cited in the file of this patent UNITED STATES PATENTS 2,488,867 Judson Nov. 22, 1949 2,488,875 Morley Nov. 22, 1949 2,625,013 Howard et al. Ian. 13, 1953 

